This invention relates to a composition of matter comprising a heat-sensitive primary backing, an integral foam secondary backing for same and a process for producing same. In particular, the invention relates to the application of vinyl foam backing to a heat-sensitive primary backing for carpeting and upholstery materials.
The application of a foam backing to a heat-sensitive material has ordinarily been accomplished by the use of adhesives. Thus, a foam layer is usually attached to a heatsensitive material by coating either the heat-sensitive material or the foam layer, or both, with an adhesive and allowing the adhesive to cure, thus adhering the layers. It has heretofore not been possible to fuse an unblown vinyl plastisol to a heatsensitive material and then heat the composition in order to foam the vinyl plastisol, since the heat at which the fusion and foaming of the plastisol occurs is oftentimes greater than the heat-sensitive backing or the carpet facing material will stand. Thus, in the carpeting industry, it is usual to apply a foamed vinyl backing to a carpet by the use of adhesives.
The use of steam to gel a mechanically frothed rubber latex on the backing web of a carpet is known. Thus, U.S. Pat. No. 3,281,258 discloses a method whereby a frothed latex is applied to a carpet backing and steam is applied against the carpet face in order to gel the latex in such a manner that gelatin proceeds from the backing/latex interface to the top of the latex. The steam temperature is about 90.degree.-115.degree.C. Such temperature is, however, insufficient to fuse and expand a vinyl plastisol containing a chemical blowing agent.
The use of high velocity, heated air to heat thermoplastics preparatory to laminating same is disclosed in U.S. Pat. No. 3,210,227 but it is not contemplated therein to fuse and expand a vinyl plastisol containing a blowing agent to a heat-sensitive backing material.
It has now been found that vinyl plastisols containing chemical blowing agents may be applied directly to a heatsensitive material, such as polypropylene primary carpet backing, and then heated to the temperature necessary to fuse and expand the vinyl plastisol while at the same time not damaging the carpet face or the heat-sensitive backing thereof.